Generally, the band gap decreases with increasing temperature. And bulk cubic CdS is known to have the band gap of 2.42 eV (at room temperature). I can't find a proper explanation related to the variation of its bandgap with temperature in literature and they mostly concentrate on the impact of nanoscale on band gap. Please, explain the reason.
In general, disorder in the crystal can change the apparent band gap and as crystallinity increased with increasing annealing temperature, the band gap is decreased . The temperature may changes the spacing between atoms and the band gap will change .i.e. the lattice constant in a crystal will change the band gap.
I am thankful for your valuable answer just I would like to add one thing that in my case, whatever the matter you have mentioned above may be viewed as just when we will precisely know the mechanism between temperature and bulk band gap of CdS i.e why the band gap is known to be 2.4 at room temperature. That means if the temperature is expanded or diminished of the bulk form it may be unquestionably changed yet what amount and from which mechanism? What would be the possible explanation?
The variation of the bang gap with temperature is very well known. It is related with two mechanisms: the electron-phonon interaction and the variation of the volumen of the unit cell.
Please see the reference in attach
Best regards,
Pedro
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